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|Alle Autoren:||John D Lynch|
|Anmerkungen:||FIGURE 1. Distribution of Rana blairi in Nebraska. Anticipated distribution is hatched. Solid symbols: specimens examined; open symbols: literature records.
FIGURE 2. Distribution of Rana pipiens in Nebraska.
FIGURE 3. Distribution of zones of sympatry of Rana blairi and R. pipiens in Nebraska. Solid circles: actual sympatry. Triangles and square: sympatry reported by Dunlap and Kruse (1976) and Pace (1974). Open circles: probable sympatric occurrences.
FIGURE 4. Distributions of Rana blairi and R. pipiens in middle and lower portions of the Elkhorn River drainage in northeastern Nebraska. Circles: (open--R. blairi only, solid--R. pipiens only). Triangles: sympatric occurrence (solid--R. pipiens predominates, open--R. blairi predominates, half-solid-equal abundance).
Extensive collecting of leopard frogs (Rana blairi and R. pipiens) in Nebraska reveals that the large zone of sympatry heretofore recognized in central and eastern Nebraska is fragmented. Rana pipiens occurs as disjunct populations on the isolated Sandhills formations in south-central Nebraska. Within the largest zone of sympatry (in northeast Nebraska) hybridization is infrequent (hybrids comprise usually less than 5% of the pooled populations). Ecologic isolation is in part effected by selection of different substrates by the two species. Rana blairi occurs in loess soil areas whereas R. pipiens predominates in areas of sandy soils.